1. Field of the Invention
The present invention relates to an information processor having a high density and a large capacity.
2. Related Background Art
In an atomic force microscope (hereinafter referred to as "AFM") which is a new type of microscope invented in recent years, a cantilever, (an elastic member) supporting a probe which is brought close (i.e. within a distance 1 nanometer or less) to the surface of a sample, is deflected by a force generated between the sample and the probe. This force is conversely measured from the deflection, and the surface of the sample is then scanned, while the distance between the sample and the probe is controlled so that the force may be constant, thereby observing the three-dimensional shape of the surface with a resolution of a nanometer or less [Binnig et al., Phys. Rev. Lett. 56, 930, (1986)]. The sample to which AFM can be applied does not have to be conductive, in contrast to a sample for a scanning tunneling microscope (hereinafter referred to as "STM"). According to AFM, an insulating sample, particularly a semiconductor resist surface or a biopolymer, can be observed in an atomic/molecular order, and so it is expected that AFM will be utilized in many fields. As systems for detecting the deflection of the cantilever, there have heretofore been an optical lever method which entails radiating light from the back side of the cantilever, measuring a position deviation of its reflected light spot, and then calculating the lever deflection from the measured position derivation; and a tunnel current method which comprises bringing a conductive probe close to the back surface of the cantilever, controlling the position of the conductive probe so that the tunnel current flowing therebetween may be constant, and then calculating the cantilever deflection from a control variable.
One information processor to which AFM is applied is a high-density large-capacity information processor. This is one of reproduction methods corresponding to a high-density large-capacity recording process in which the shape of a recording medium surface is locally changed. This kind of high-density large-capacity information processor utilizes the principle of the above-mentioned AFM, and in this processor, the cantilever, supporting the probe brought close to the site where the shape change locally occurs, is deflected under the influence of a force generated between the local site and the probe. The deflection is then detected, whereby the reproduction is carried out. Furthermore, as a similar apparatus, there has been suggested a recording detector in which the principle of AFM is applied to the position control of the probe in the high-density large-capacity information processor having the principle of STM.
However, in the case that one probe (a probe electrode) for the reproduction is used in each of the above-mentioned conventional examples, a long period of time is taken for the reproduction and therefore their practicality is limited. Accordingly, it is essential to use multiple probes. However, in the conventional method for detecting the deflection of the cantilever supporting the probe, the constitution of the apparatus is enlarged and the use of multiple probes is difficult.